a little jetting help please

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finally got my brother's 250r running.

anyways, we seem to be running into some jetting problems. we've got an LRD pipe and a UNI filter with the lid on for the real mods to it that would affect the jetting and it seems like it's running rich with a 152 in it? it bogs once in a while and the plug looked decently dosed

bad plug? running rich? help me out here. i'm not much of a 2-stroke guy

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also, isn't stock like 150-158? why would it be running rich with a pipe and filter?

[250r4life]

whats your elevation? temperature? humidity?

what plug? what 2 stroke oil at what mixture?

what carb are you running? still on stock bore? ported?

we need a bit more information...

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well im in illinois. i dont know what the elevation is here. it's a little chilly outside

i think the plug is a br8es. klotz mixed at around in between 20:1 and 32:1. going to start mixing at 32:1 from now on.

the carb is the stock keihin flatslide one. stock bore, no porting.

[250r4life]

well there could be your problem right there... if you were running anywhere close to 20 to 1, with a small jet, youre not getting very much fuel...

get your oil to 32:1, then put a new plug in, and come back and let us know the results...

[Scott-300ex]

Stock is 148 I am very sure of it.

152 sounds real good with like a 45 pilot.

But 20:1 with Klotz is WAY to rich. I would say 32:1 or 40:1.

How much smoke are you shootin out?

[250r4life]

Originally posted by Scott-300ex
Stock is 148 I am very sure of it.

152 sounds real good with like a 45 pilot.



theyre you go again poppin' off about things you know nothing about...

he was right, stock is from 150-158 depending on the year...

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okay i'll make sure my brother runs 32:1 or higher next time and i'll get a new plug.

[250r4life]

i wouldnt go anything less than 40:1..

i think you should stick to 32:1 myself...

[criminalpoet]

I dont exactly know what your particular set up is but if you really want to know what your bike needs then start doing some plug chops. As far as the pilot jet goes as a rule of thumb if you have to go more than 2 turns out on the air screw to get it to idle right then you need to drop 1 size on the pilot jet. If you need to go in more than1 turn then you need to go up 1 size on the pilot jet.
Once you get that dialed in your good from idle to 1/8 throttle.

Next it would be time to dial in your needle clip position, to do this you need to find a long dirt road and let the bike warm up. Once its warmed up jump on it and ride it at the 1/2 throttle position while counting to 20. At 20 seconds pull the clutch in and kill the power. Pull the spark plug and check the color, if its white, grey, or slightly yellow then your running lean and you need to go down 1 needle clip position. If the color on the plug is black or really oiley then you need to go up 1 needle clip position as this would mean your running rich. The ideal color that you want to look for on your plug would be a med. to dark brown, or coffee color.

After the needle clip position is squared away then its time to set your main jet size. To do this you need a really long dirt road lol, because you need to ride your bike in 6th gear maxed out. Count to 15, pull the clutch in and kill the power, come to a stop immediately and pull the plug. Check the color just as you did when you were setting your needle clip position, the same principles apply.

It all may seem like a lot to do but actually its very easy. The more you do it the easier it gets, I can dial pretty much any bike in in 30 minutes or less. A couple of other things your going to want to do is use a brand new plug for this process and definitely start mixing at 32:1 unless its a full synthetic then I would go 40:1. Sometimes with a full synthetic, depending on the brand, mixing to rich causes the spark to be masked to much thus hurting performance and fouling plugs. It also causes a huge amount of carbon build up in your motor. Something to keep in mind as far as your jetting goes is usually changes in gearing means changes in jetting. I know on my R when I drop a tooth on the front I also have to drop 1 main jet size too. When I go up 1 tooth on the front I also have to go up 1 size on the main jet. The needle clip position generally isnt so tempermental.

Anyways good luck with it man!

A friend in the quads,
Jose from Albuquerque

[250r4life]

would you be so kind as to explain why when you change sprockets would you have to change jets...

[criminalpoet]

It changes the load on the motor. Think of it in terms of riding a mountain bike, when you drop down a gear it requires less of an effort to pedal. But when you go up a gear it requires more of an effort to pedal. How does this apply to a 2 stroke motor? Well, going down a gear would make it easier for the motor to turn, which means it would need less fuel/oil to achieve this. When you go up a gear it would require more of an effort for the motor to turn it, which would mean it would require more fuel/oil to turn it.

When a 2 stroke needs more, or less power for a given situation it looks to air and fuel for that power. You would adjust depending on that load requirement.

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jesus, i hate 2-stroke jetting haha

i think i may just drop it off at the mx shop near me. i'm on good terms with the guy so i'm sure he could help me


thanks guys

[250r4life]

Originally posted by criminalpoet
It changes the load on the motor. Think of it in terms of riding a mountain bike, when you drop down a gear it requires less of an effort to pedal. But when you go up a gear it requires more of an effort to pedal. How does this apply to a 2 stroke motor? Well, going down a gear would make it easier for the motor to turn, which means it would need less fuel/oil to achieve this. When you go up a gear it would require more of an effort for the motor to turn it, which would mean it would require more fuel/oil to turn it.

When a 2 stroke needs more, or less power for a given situation it looks to air and fuel for that power. You would adjust depending on that load requirement.

i understand your logic in the matter, i just dont know if its accurate or if i agree with it... im not saying its innacurate, but there is something in the back ok my mind thinking its not... I'm gunna have to think about that one...

[Scott-300ex]

Originally posted by 250r4life
theyre you go again poppin' off about things you know nothing about...

he was right, stock is from 150-158 depending on the year...

Are you honestly 2 years old?

You spend 50 hours a week trying to talk $h!t, well hey, I DON'T CARE. I have a life I don't need to feel accomplishment by flaming people on the internet. Just grow up and shut up

And I guess Clymers is wrong cuz Its between 144 and 148 for years, they wouldn't have a 8 difference in them.

Go Away!!!!!!!!!

[250r4life]

you are seriously unintelligent...

i have the clymer manual... thanks...

[criminalpoet]

Originally posted by 250r4life
i understand your logic in the matter, i just dont know if its accurate or if i agree with it... im not saying its innacurate, but there is something in the back ok my mind thinking its not... I'm gunna have to think about that one...

Well my friend its a fact! Talk to any builder or seasoned tuner and they'll tell you the same. But, I wouldnt encourage you to think about it at all man, I say go out and litterally put it to the test and youll see. Sure your bike will run fine going up or down a tooth without changing the jetting. But it will run A LOT better if you do.